1. Field of the Invention
This invention relates to a substrate for an ink jet recording head, an ink jet recording head having such a substrate and methods for preparing them.
2. Related Background Art
An ink jet recording method is a recording method which performs recording by discharging an ink (liquid for recording) through discharging openings provided on a recording head and depositing this onto a recording medium such as paper, etc., and offers many advantages such that generation of noise is very small, and also high speed recording is possible and yet no specially formulated paper for recording is required, etc. and various types of recording heads have been developed.
Among them, the recording head of the type which permits heat energy to act on ink, thereby discharging the ink through discharging openings has advantages such as good response to recording signals and easy arrangement of multiple discharging openings at high density.
The recording head to be used for such a recording method has typically a construction as shown in the schematic perspective view of FIG. 1. Specifically, it is provided with a discharging opening 101 provided for forming flying droplets by discharging ink and a liquid channel 102 for supplying ink communications with the discharging opening. An electricity-heat converting element having a heat generating resistor which is a heat energy generator 104A is provided internally of the liquid channel 102, and electrodes for supplying current to the heat-generating resistor and a liquid chamber 103 for storing ink to be supplied into the liquid channel are provided on the upstream side of the liquid channel. In addition, a recording head can also be provided with, if necessary, a protective film having the property of enhancing ink resistance of the electricity heat converting element.
Such a head is generally prepared as shown in FIG. 2. FIG. 2 shows schematic sectional views of the preparation steps at the position when the recording head is cut at the II-II' portion shown in FIG. 1. First, the layer 251, a part of which becomes finally the heat-generating resistor (hereinafter called the heat-generating resistance layer), and the layer 252 a part of which becomes the electrodes (hereinafter called the electrode layer), are formed on a support 253 (steps (a), (b)). Then, the electrode layer 252 is subjected to patterning utilizing a photolithographic technique by use of photoresist 254 and an etching technique, and subsequently, the heat-generating resistance layer 251 is similarly subjected to patterning to form the heat-generating resistor and electrodes (steps (c) to (k)). Specifically, on the product (b) after completion of the step (b) is laminated a photoresist 254 such as photosensitive resin, etc. (step (c)), the photoresist 254 of the product (c) is subjected to pattern exposure (step (d)), followed by developing of the photoresist 254 of the product (d) (step (e)). By the step (e), the photoresist 254 has any unnecessary portions removed to produce a desired pattern shape. Next, the electrode layer 252 exposed on the product (e) is removed by etching (step (f)), and the remaining resist portion 254' of the product (f) thus prepared is removed (step (g)). Thus, a desired pattern of the electrode layer 252 is formed.
The pattern of the heat-generating resistance layer 251 is also formed according to the same steps as in the case of forming the pattern of the electrode layer 252. That is, the pattern of the heat generating resistance layer 251 is formed by lamination of the photoresist 254" (step (h)), pattern exposure on the photoresist of the product (h) by use of a photomask (step (i)), developing of the photoresist 254" subjected to pattern exposure of the product (i) for removal of unnecessary portions (step (j)) and etching of the exposed heat-generating resistance layer 251 of the product (j) (step (k)). Then, the resist 254'" is peeled off (step (l)). Next, after a protective film 255 having the property of ink resistance, etc. is formed (step (m)), a photosensitive resin 256 is laminated (step (n)), followed by exposure (step (o)) and development (step (p)), to form a wall 256' with the hardened film of the photosensitive resin subjected to patterning ((m) to (p)). This wall constitutes the liquid channel wall which can be filled with a liquid. Next, on the wall 256' is adhered (plastered) a ceiling 257, and thereafter a discharging opening is formed by cutting (not shown) to complete an ink jet recording head (step (q)).
Thus, the preparation method which has been used in the prior art comprises many steps, and in addition, it takes a long time for some of the steps, particularly the etching step. It has been recognized that too much preparation time is required. Also, there is room for improvement from the point that the positional precision of the individual members is worsened, because the number of patterning steps is high.